Casey Fury, 24, pleaded guilty to two counts of arson. Prosecutors said he set a fire aboard the USS Miami on May 23.

"There were physical and emotional injuries to five first responders who risked their lives going into what had to be the equivalent of a roaring blast furnace," said U.S. Attorney Tom Delahanty.

Two crew members and five firefighters were hurt, including a close call for a Rye firefighter rescued after a flashover.

The fire burned for hours and wasn't put out until a day later. Fury admitted setting that fire and another one on a dock on June 16 that together caused more than $450 million in damages.

"It's the kind of situation that in an enclosed area like that, I would feel common sense would say there's a potential for extreme risk to people and damage," Delahanty said.

When investigators with the Navy first interviewed Fury, he denied any involvement, but in a later interview, he admitted to setting the smaller fire on a dock outside the submarine. Later, he admitted setting the first fire in May.

Investigators took Fury aboard a similar attack sub, the USS Pasadena, to show how he started the fire, and then they again asked him to demonstrate on board the charred USS Miami.

Fury said he set the fire so he could get out of work early.

"At approximately 5:30 p.m., he went up to the stateroom area at midlevel and he set some rags on a bunk on fire with a lighter and then returned to paint stripping in the torpedo room area," Delahanty said.

He could face life in prison for the first fire alone, but under a plea deal, he is expected to get a sentence of 15 ½ to 19½ years in prison. He will also have to pay restitution.

"We have to look at what is fair under the circumstances," Delahanty said. "The life sentence is the statutory maximum. In this case, there are many factors the court will take into consideration, and I think it's reasonable with the facts of this case that he not be getting life."

Rye Fire Chief William "Skip" Sullivan said the case was handled quickly and properly, but he considers the recommended sentence to be light, given the circumstances.

"I think he got off pretty light, considering the injuries to the ship's crew, the Rye firefighter who was injured and out of work several weeks and the damage he did to the reputation of the Portsmouth Naval Shipyard," Sullivan said.

Delahanty said there will be attempts to collect what restitution can be made, but the amount of damage done exceeds what almost anyone would be able to pay back.

Delahanty said he expects the judge won't have a sentencing decision until March at the earliest.